BENICIA, Calif. (AP) – Two whales lost in the Sacramento River were spotted Tuesday morning just beyond a bridge where they had stopped a day earlier, a delay that worried scientists hoping to get them back to the ocean.

Biologists hope the mother humpback whale and her calf reach more brackish water soon to help ease the physical strain they have suffered from long exposure to fresh water.

They were particularly concerned about wounds and new lesions on the humpbacks’ skin and were awaiting test results to determine the cause. Antibiotics were injected into the whales on Saturday to try to slow the damage from the gashes, likely from a boat’s keel.

The two whales spent Monday near the Benicia-Martinez Bridge, about 45 miles from the Pacific before finally swimming past it Tuesday. They were first spotted May 13 and got as far as 90 miles inland to the Port of Sacramento before turning around.

Memorial Day sightseers swarmed the waterfront to catch a glimpse, while the U.S. Coast Guard worked to maintain a 500-yard safety zone around the whales.

About 100 boats carrying would-be whale watchers surrounded the pair as news of their location traveled. Coast Guard crews hauled several swimmers out of the water as they tried to approach the whales, Lt. Larry Curran said.

Despite the pair’s health problems, officials did not plan to take any action to prod them toward the Golden Gate Bridge. They also said they could not predict when the whales might move again.

“It’s still anybody’s guess. The whales are going to decide what they’re going to do and how they’re going to do it,” said Bernadette Fees, deputy director of the California Department of Fish and Game.