Catholic churches in southern New Jersey are taking extra precautions since the Diocese of Camden received a letter saying biological agents would be placed in holy-water fonts and ventilation systems, a diocesan spokesman said Tuesday.

The diocese received an anonymous letter last week threatening to put biological contaminants in Catholic churches in New Jersey, said Andrew Walton, a spokesman for the diocese. The letter, which was mailed May 1 and has a Bellmawr postmark, was received in the Camden office May 4 and opened May 5.

The letter has been turned over to the Camden County Prosecutor's Office, which is investigating the incident, Walton said.

"We believe every threat has to be taken seriously," and pastors and church administrators were told of the letter and warned to be vigilant about people on their properties, Walton said. Anyone who sees something suspicious on church property is asked to call local police.

Church officials hope the letter is a hoax and that the writer has no intention of carrying out the threats, Walton said. But diocesan officials thought it necessary to warn parishes and inform the prosecutor.

The fonts are placed at church entrances for worshippers to dip their hands in before making the sign of the cross, Walton said.

At least one Atlantic County church made an announcement of the threats to those attending Sunday Mass.