An executive of Mace Security International Inc., the Horsham company that operates car washes in Pennsylvania and New Jersey, pleaded guilty yesterday to immigration-violation charges over the hiring of illegal immigrants.

Robert Kramer, 56, pleaded guilty in federal court in Philadelphia yesterday to knowingly employing at least 50 illegal immigrants who were not authorized to work in the United States, federal prosecutors said yesterday in an e-mailed statement.

Kramer is the general counsel of Mace Security, which is best-known as a manufacturer of self-defense sprays, and he also is the chief operating officer of the company's car wash unit, prosecutors said.

Kramer is facing a maximum sentence of six months in prison and a $150,000 fine.

"Car Care officials hired undocumented workers, gave those workers the names of former employees, and then paid the undocumented workers with checks in the names of the former employees," prosecutors said in the statement.

Mace Security, which had been based in Mount Laurel, moved last year to Fort Lauderdale, Fla., and then, later last year, moved back to the Philadelphia area.