A fisherman reported seeing what appeared to be a body in Upper Otay Lake Monday afternoon.
The sighting at the reservoir east of Chula Vista was reported shortly after 2 p.m., according to police.
Officers investigated and, unable to confirm or discount the report, called in city lifeguards.
By the time the dive team got to the lake, however, it was getting too dark an effective underwater search, said Jose Ysea, a spokesman for the San Diego Fire-Rescue Department.
The divers planned to return for a thorough search on Wednesday, Ysea said.
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