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MANSFIELD - Sophisticated thieves - almost certainly professionals, police say - broke into a pharmaceutical distribution warehouse in the Cabot Industrial Park over the weekend, stealing 300,000 pills described as controlled substances.

Police Chief Arthur O'Neill said the thieves disabled the alarm system and entered the AmerisourceBergen Corp. warehouse at 101 Norfolk St through the roof. The break-in was discovered about 7:30 p.m. Sunday, he said.

"They had enough sophistication to disable the alarm system," O'Neill said.

The company also has surveillance cameras which were also disabled, the police chief added.

He said he could not estimate the dollar value of the missing drugs. "There is a tremendous amount of drugs out there that are unaccounted for," O'Neill said.

O'Neill said local detectives are being assisted in the investigation by crime scene specialists from the FBI and agents with the U.S. Drug Enforcement Administration.

Other details of the theft were not released.

The Pennsylvania-based company is the largest pharmaceutical distributor in the United States, according to the company's Website.

The company reported a record operating revenue of $56.7 billion in its last fiscal year, which ended Sept. 30.

No one answered the telephone at the company's facility in Mansfield Monday afternoon. No one returned a message left at the company's corporate headquarters.