Two Japanese scholars drowned and another was missing after an inflatable boat carrying nine people on a research trip organized by the University of California at Davis sank Monday night in the Gulf of California, local police said Tuesday.

Takuya Abe, a 55-year-old professor at the Center for Ecological Research at Kyoto University and one of the world's leading termite experts, and Shigeru Nakano, a 37-year-old associate professor at the center, were killed in the accident. Masahiko Higashi, 45, another professor at the center, is still missing, according to police.

In addition to the two Japanese, the body of a U.S. graduate student has been recovered. Gary Polis, the expedition's leader and a U.S. expert on spiders, is also missing.

Four people, including students, swam to a nearby island after the boat sank at 10:30 p.m. off the coast of Baja California in Mexico, police said. The four were rescued Tuesday.