Two humpback whales, believed to be a mother and her calf, that wandered from San Francisco nto the Sacramento river had arrived at the outskirts of the state capital Wednesday morning. "We're going to do a health assessment of the animals, probably visually," said Connie Barclay, a spokeswoman with the National Marine Fisheries Service. "We may get a clue as to why they are there."

According to media reports, the whales were first spotted Sunday in the lower Sacramento River, drawing hundreds of onlookers the following day when they surfaced repeatedly near the delta towns of Isleton and Rio Vista. The U.S. Coast Guard has been broadcasting the position of the whales, requiring that recreational boaters stay at least 100 yards away from them, said spokeswoman Lt. Amy Marrs.

Authorities are hoping the pair will turn around on their own and head back to sea. But if the whales get stuck, marine biologists will try to herd them back to open water using underwater sounds that mimic the call of a humpback whale.