Federal agents raided several Southern California museums on Thursday in search of Southeast Asian antiquities that are believed to have been illegally obtained, smuggled into the U.S. and sold at inflated prices so sellers could claim fraudulent tax deductions after donations to the institutions.

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Agents also investigated American Indian artifacts at one museum.

Search warrants were executed at the Los Angeles County Museum of Art, the Bowers Museum in Santa Ana, and the Mingei International Museum in San Diego, said Virginia Kice, a spokeswoman with Immigration and Customs Enforcement.

A search warrant also was issued for the Pacific Asia Museum in Pasadena.

Authorities said no arrests had been made and no charges had been filed.

Court documents portray a five-year scheme in which the owner of a Los Angeles art gallery worked with a smuggler to bring in artifacts from Thailand and China, offered them as charitable contributions and then tried to claim the donations as tax write-offs by boosting their value. In some cases, museum officials initially questioned how the artifacts were obtained but eventually accepted them, according to affidavits filed in support of the search.

The investigation is the latest public relations debacle for museums in the United States that have been accused by foreign governments of housing treasures stolen from their countries. Italy has been negotiating with various museums, including the Metropolitan Museum in New York and the J. Paul Getty Museum in Los Angeles, to have various statues, vases and other items from Roman and Greek times returned.

Representatives from the Mingei and Pacific Asia museums did not return phone calls seeking comment.

LACMA spokeswoman Allison Agsten said in an e-mail that the museum was cooperating with the investigation.

A statement from the Bowers Museum said items on display from El Malpais National Monument and Chaco Culture Historic Park in New Mexico were being examined by agents as to whether they were removed without a permit. Items from the Ban Chiang area in Thailand also were being reviewed.

The warrants stem from an undercover investigation by a National Park Service special agent who posed as a collector interested in various artifacts. The agent targeted Robert Olson, who is alleged in an affidavit to be a smuggler, and Jonathan Markell, who co-owns an Asian art gallery in Los Angeles with his wife.

Court documents said the couple and the agent met more than a dozen times and regularly e-mailed and called one another about the "sale, importation, and donation of stolen archaeological resources from China and Thailand and antiquities illegally imported from Burma." Some of the calls and meetings were recorded, the warrants said.

In the case of the Pacific Asian Museum, Jonathan Markell and the agent met with museum staffers in March 2006 to donate items recovered from the Ban Chiang culture in northeast Thailand. Two museum officials questioned the agent about how one of the artifacts was obtained. After Markell assured them that the Thai government wouldn't miss the item because it wasn't "an earth-shattering piece," the museum accepted the donation, the documents said.

A phone and e-mail message left for Markell wasn't immediately returned. Olson could not be immediately located for comment.

The warrants also detail a relatively simple scam in which Markell allegedly sold antiquities worth a few hundred dollars at a markup to the undercover agent and then used false appraisals to increase the value of the pieces to just less than $5,000 — the Internal Revenue Service's floor for requiring written appraisals to support tax deductions on donated art.

At the Mingei in San Diego, museum officials accepted five Ban Chiang ceramic vessels, along with two other pieces, in June 2006. The undercover agent allegedly paid $1,500 to Markell, who declared a value of nearly $5,000 to the museum, according to the warrants.

Markell allegedly sent an e-mail to Mingei director Rob Sidner claiming that his Ban Chiang pieces had come from a now-deceased former curator at the Los Angeles County Museum of Art, and were all imported before Thai export restrictions went into effect.

Olson allegedly told the agent that he was being sent Ban Chiang antiquities as they were being dug up in northeast Thailand, in violation of Thai and international law.

It was unclear in court documents whether Mingei officials were aware of the provenance of the artifacts it accepted.

With the Los Angeles County Museum of Art, Markell allegedly told the agent he lied to museum officials so they would accept his items. He allegedly also indicated museum officials had found a "loophole" to import restriction on some items but couldn't elaborate.

According to the court documents, the agent who worked with Markell said he didn't seem worried about being caught. The agent said that after providing Markell a news article about someone getting arrested for false tax returns dealing with antiquities, the dealer shrugged it off and laughed.

The documents quoted Markell as saying that "people who had been caught had to have done something stupid."