A Russian man who was being detained in an immigration jail on Otay Mesa died Sunday night after being found not breathing in his bunk, according to the Immigrations and Customs Enforcement agency.

The dead man was identified as Igor Zyazin, who was arrested by ICE on April 24 trying to enter the country at the San Ysidro port, officials said. He was taken into custody after Customs and Border Protection officers determined he had previously been deported in 2009.

The cause of death has not yet been determined by the San Diego County Medical Examiner, according to a statement from the agency.

Zyazin was found by a guard just before 9:30 p.m.. Personnel at the jail tried to revive him until paramedics arrived. He was pronounced dead around 10 p.m. while en route to the hospital, the agency said.

The Otay Mesa Detention Facility is operated by Corrections Corporations of America, the largest private jail company in the country, under a contract with ICE. The facility has a capacity of 1,040.

Zyazin is the sixth person to die in ICE detention facilities around the country since the start of the federal fiscal year on Oct. 1. There were seven deaths reported in ICE detention facilities for the previous fiscal year, according to government data.

The agency has come under scrutiny from immigrant rights groups and some members of Congress over the number of deaths of immigrants in custody. A report by Prison Legal News last year counted five deaths at the San Diego facility since 2004, all attributed to underlying medical problems or natural causes.

At the time of his death Zyazin’s case was pending and he was awaiting an interview with a U.S. Citizenship and Immigration Services officer. The ICE statement said he had no criminal record in the U.S. The reasons for his deportation in 2009 could not be determined.

Both his next of kin and the Russian consulate were notified of the death.