The nation's second-largest prison system is enforcing a lockdown after authorities learned a condemned killer had made threatening calls to a Texas state senator from a cell phone smuggled into death row.

Gov. Rick Perry on Monday ordered the lockdown of the state's 111 prisons and a systemwide search for contraband.

The condemned inmate's 60-year-old mother was arrested and accused of buying minutes for the phone, and investigators said more arrests were expected. Perry's office said the phone was smuggled into prison by a bribed corrections officer.

Authorities learned about the phone after inmate Richard Tabler called Sen. John Whitmire and told him he knew the names of the legislator's daughters and where they lived, said John Moriarty, the prison system's inspector general.

Tabler shared the phone with nine inmates on his cell block, and prison officials said about 2,800 calls were made on it during the past 30 days.

"Let there be no doubt about how seriously we take this security breach," Perry said, directing prison officials to impose the lockdown that will keep the state's 155,000 inmates from receiving visits and tighten security checks for all prison employees.

Whitmire, chairman of the state Senate Criminal Justice Committee, summoned prison administrators to Austin for an emergency meeting Tuesday of his criminal justice panel to address what he called "a lax attitude on contraband."

"I want to know how an inmate on death row gets a cell phone in the first place, and then how they and other inmates can make thousands of calls in a month without getting caught," Whitmire told the Austin American-Statesman newspaper.

Richard Tabler's call to Whitmire on Oct. 7 prompted the investigation. The prisoner's calls continued intermittently, the latest coming Sunday, according to investigators. In the calls, Tabler told Whitmire he knew the lawmaker's daughters, their ages and their addresses.

Tabler has been on death row since last year for a shooting spree in which two men and two teenage girls were killed in central Texas during Thanksgiving weekend 2004. The four victims had ties to a strip club there.

Early this month, Tabler was in court telling a judge he wanted to end appeals and volunteer for execution.

Perry's office said a bribed corrections officer was believed to be the source of the phone. The officer's name and whether he or she had been apprehended were not disclosed.

The prison system's inspector general said each of the 2,800 calls from the phone would be investigated. The phone has been confiscated.

Lorraine Tabler was apprehended Monday at Austin's airport as she arrived for a scheduled visit with her son.

She was held on felony charges of providing a prohibited item to an inmate. It was not immediately known if she had an attorney. Messages left at a phone number for her in Blackshear, Ga., were not immediately returned.

A total of 44 calls were made on the phone to Lorraine Tabler's home number, according to the arrest warrant affidavit. The same phone was used to call Whitmire.

The investigation determined calls were coming to the phone as well as going out.

Investigators said the phone had been purchased in Waco in September 2007 and that Lorraine Tabler had been buying time for the phone, including a purchase on Oct. 7 at a Wal-Mart store in Waycross, Ga. Detectives obtained a store video showing her making the purchase.

Moriarty said the phone apparently was being passed among the other nine inmates in Tabler's immediate cell block area. Like Tabler, they also face possible criminal charges or disciplinary actions.

Illegal cell phone use is a continuing problem in prisons where the phones are considered a security breach and of particular value to gang members.

Moriarty said since Jan. 1, his investigators have closed or are working on 19 cases of prohibited phones or phone components on death row. He said about 700 reports of prohibited phones were investigated systemwide this year, including one in which officials have an X-ray of an inmate with a phone and charger inside the prisoner's body.