LAWRENCE, Ind. -- A Lawrence boy became ill after opening a envelope that may have contained powder Friday night, prompting emergency personnel to take him and three relatives to a hospital, officials said.

No irritants appeared to be on the envelope, but investigators will take a closer look, the county health department said.

Officials said the boy went to a mailbox at his home in the 7600 block of Geist Estate Drive, saw an envelope addressed to him and opened it. Powder came out of the envelope and made the boy sick, his mother told police.

The mother called 911, and hazardous-materials personnel responded, setting up a tent where the mother and two other relatives were decontaminated even though they weren't ill, 6News' Cheryl Jackson reported.

The boy and the other three were taken to a hospital; information on the child's condition and details about his illness weren't available.

Postal inspectors were investigating the incident. Officials said the envelope had no return address.