A boat packed with Mexican migrants collided with a U.S. Customs and Border Protection vessel off the Southern California coast Thursday, causing it to capsize and killing a woman on board, U.S. authorities said.

The collision also left one person from the boat seriously injured and two more with minor injuries, Mexico's Foreign Relations Department said in a statement that also called for an investigation.

The patrol boat spotted the suspected human smuggling boat near Encinitas in San Diego County before dawn and ordered it to stop. The 20 people on board were suspected of trying to enter the country illegally, said Jackie Wasiluk, a CBP spokeswoman.

Agents ordered the boat to stop and fired warning shots but the 26-foot vessel ignored them, she said.

The two boats collided. The suspected smuggling vessel capsized, tossing everyone into the water, and sank.

The CBP crew pulled people from the water. An unconscious woman was airlifted to a hospital, where she died, authorities said.

The others were taken into custody, including the three injured who were taken to hospitals.

It was not immediately clear whether the smuggling boat hit the patrol boat by accident or on purpose.

Smugglers often use small boats, known as panga boats, to smuggle drugs or people from Mexico into the U.S., avoiding heavily patrolled ground border areas. In recent years some boats have been found as far north as Central California.

The journey is a risky one and confrontations with U.S. authorities have turned deadly.

Last year, a Mexican man was sentenced to life in federal prison for ramming his 30-foot boat into a Coast Guard craft in 2012 during an anti-smuggling patrol off Santa Cruz Island in Southern California. The collision killed a Coast Guard crewman.

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This story has been corrected to take out references to Border Patrol agents because they only work on land.