Rescue crews are trying to find a woman who disappeared after she jumped into Lake Ray Hubbard.

Dallas Fire-Rescue said the woman, whose name has not been released, had been on a pontoon boat near Rockwall Harbor with three other people.

Witnesses said the woman jumped into the water and resurfaced for a short time before going back under. She never resurfaced again.

Investigators said there were life jackets on the boat, but the woman was not wearing one.

Sonar equipment was being used in the search. Dallas Fire-Rescue personnel said they will continue to search until midnight and will return to the lake Sunday morning if the woman has not been found.