Four U.S. Border Patrol agents were indicted yesterday on charges they beat and abused illegal Mexican aliens who had just stolen their way across the U.S.-Mexico line on southern California.

It is the first time criminal charges have been lodged against agents of the U.S. Immigration and Naturalization Service.

The indictment, returned in U.S. District Court in San Diego, charges the four agents were involved, either jointly or independently, in beatings of at least three illegal aliens on July 3, July 4 and Aug. 1, 1979. At least one of the agents also allegedly tried to cover up the activities when the Ustice Department opened an investigation.

The extent of injury to the aliens could not be determined because the INS agents dumped them on the Mexican side of the boarder following the beatings, officials said.

Named in the indictment were Border Patrol agents Jeffrey Otherson, charged with four counts, and Bruce Brown, Dirk Dick and Daniel Charest, each named in three counts charging civil rights violations.

Outgoing Immigration Commissioner Leonel Castillo said he was placing all four on 10 days' administrative leave while the indictment is reviewed to determine what further action might be necessary.

The indictments said the agents did not report the encounters to their supervisor or file written reports.

The indictment said Dick allegedly tried to cover up the incidents by asking fellow agents to lie to federal investigators.

All four agents were charged with conspiring to defraud the government and obstruct the lawful functions of the Boarder Patrol by unjustifiably assaulting and mistreating illegal aliens, punishable by up to five years in prison and a $10,000 fine.

The four also were charged with separate counts in the beatings, and Charest was accused of lying to the grand jury last week.