Deputies arrested a Covina man Wednesday after he brandished gun, threw a bag of drugs into a drainage ditch and led deputies on a chase from El Monte to San Dimas, authorities said.

Joel Lopez, 40, of Covina was booked on suspicion of possession of suspected methamphetamine while armed, Los Angeles County sheriff’s Lt. Edward Godfrey said.

The incident began about 10:40 a.m. when a gang enforcement deputy spotted Lopez brandish a handgun in the area of Maxson and Ferris roads in El Monte, the lieutenant said.

The deputy tried to stop Lopez, initiating a chase, Godfrey said.

Both a deputy and witnesses spotted Lopez throw something from his car into a drainage ditch at the outset of the pursuit, officials said. When deputies retrieved the tossed item, they discovered it was about an ounce and a half of what appeared to be methamphetamine.

The chase continued east on the 10 Freeway until Lopez ultimately pulled over and surrendered about 15 minutes later after exiting the freeway at Holt Avenue in San Dimas, Godfrey said.