A private investigator says he found tens of thousands of sensitive documents dumped outside a California ACORN office just days after the state attorney general announced an inquiry into the community organizing group.

Derrick Roach, a licensed investigator based in San Diego, told FoxNews.com he paid an impromptu visit to the city's ACORN branch on Oct. 9 and watched from his car as a man tossed bags of files into a Dumpster outside the building.

After ACORN staff left for the day, he says, he searched the trash bin and discovered more than 20,000 documents he believes point to illicit relationships between ACORN and a bank and a labor union — as well as confidential information that could put thousands at risk for identity theft.

"We're talking people's driver's license numbers, dates of birth, Social Security numbers, credit card numbers, bank account numbers, tax returns, credit reports" — all tossed in public view in the Dumpster, he said.

In one document shared with FoxNews.com, an ACORN employee's name, address, date of birth, Social Security number and driver's license number were revealed, and photocopies of the employee's license and Social Security card were also included. Another document showed bank account information for a woman paying an ACORN membership fee by check.

"It was just a careless disregard for the people that ACORN claimed to be helping," Roach told FoxNews.com. "They put these people at risk."

Roach said that data breach laws bar dumping like the kind he uncovered at ACORN's office. Tossing the documents into a Dumpster, he said, constitutes a crime in California.

"So if someone wanted to, they could bring legal action against ACORN for doing this," he said.

A top ACORN official in California apologized for the lapse Monday, saying that some confidential information might have been thrown away during a massive clean-up of their offices last month.

"In early October, when our San Diego staff were doing an office clean-up in preparation for a major 10-station phone bank program being set up in our offices, it appears that included in the piles of garbage being thrown out may have been some documents containing private information," said Amy Schur, state head organizer for California ACORN, in an e-mailed statement.

Schur implied that "this guy" Roach, a former Republican candidate for statewide office, may have had political motivations for unearthing the documents. She said ACORN would seek the return of the documents "so that we may give proper notice of the compromising of the information as required by law."

Roach told FoxNews.com he has been going over the trove of ACORN files and has found connections to the California Teachers Association and to Citibank.

"ACORN was acting as an agent" for Citibank, Roach charged. "They had mortgage information for homeowners ... who were in foreclosure, who were in default."

Roach says that the documents suggest that ACORN staffers would go out on "assignments" to take pictures of some residences or even to "go out and actually make contact" with people living in homes financed by Citibank loans.

He said he believes Citibank will have to report to its customers that their information may have been at risk when ACORN threw it away. "They took information and they just dumped it in the garbage," he said.

Citibank ran an outreach program through ACORN that utilized the group's local staff to encourage homeowners at risk of defaulting on their mortgages to contact the bank and work on avoiding defaults. That relationship has since been severed, a spokesman for Citigroup told FoxNews.com in an e-mail.

"Over time, Citi has worked with a variety of not-for-profit partners, including ACORN, to provide financial education, meet affordable lending needs, promote stable homeownership for low- to moderate- income consumers and help in foreclosure prevention," the spokesman said.

"We are deeply concerned about the recent media reports regarding ACORN. We recently suspended our charitable financial support and program relationships with ACORN, and we are waiting for the results of the independent audit of ACORN's activities now underway."

Roach also charged that the California Teachers Association, the state's largest teachers' union, was "funneling information to ACORN for political activity" — a relationship that he said would not be illegal but would require ACORN and the CTA to disclose fully.

"I've done some checking into the reports that have been filed for the CTA, for ACORN, and I'm not finding any of this information being disclosed," he said. He did not provide any documents illustrating the relationship to FoxNews.com.

CTA spokesman Mike Myslinksi said the union had no comment on documents it had not seen. "That's out of left field," he said.

Roach's accusation comes in the wake of a national scandal for ACORN, the Association of Community Organizations for Reform Now. Staffers were caught on tape this summer in six cities offering to help a pair of filmmakers posing as a pimp and prostitute to lie to the IRS and acquire illegal home loans.

ACORN fired an employee in its San Diego office, Juan Carlos Vera, after video surfaced of him offering to help the "pimp" and "prostitute" smuggle in girls from Tijuana, Mexico, noting that he had many contacts in the city who could assist in smuggling them across the border.

The group is now under investigation by a number of city, state and federal agencies, and Congress has cut off funding for the group.

On Oct. 1, California Attorney General Jerry Brown launched a state investigation of ACORN. It was just eight days later that Roach says he retrieved the sensitive files — timing he says he finds fishy.

"I think if you look at the timeline of events when the attorney general made the announcement, when the documents were dumped, I think that it's highly suspicious."