A sport utility vehicle belonging to a missing pregnant woman was found in a creek Monday as police searched for her and her 7-year-old son, two days after a pool of blood was found in their home.

Officers on horseback and using dogs concentrated the search in a rural area of Denton, about 30 miles northeast of Fort Worth (search), after a landowner found the SUV belonging to Lisa Underwood (search) and her son, Jayden. The vehicle was nose down and partly submerged in a creek.

A statewide Amber Alert (search) was issued after the woman failed to show up for her baby shower Saturday, and the alert was expanded to New Mexico, Oklahoma, Arkansas and Louisiana.

Police would not give details of what they found at Underwood's Fort Worth home, but a police report said relatives checking her house Saturday found a large pool of blood on the living room floor.

There were no signs of forced entry, Lt. Gene Jones said.

Authorities had few new details Monday, saying they could not discuss specifics because of the ongoing investigation.

Sgt. Rene Kamper said the keys to Underwood's vehicle were found near the SUV but she declined to say what, if any, other evidence was found.

"There are a lot of questions we have. We haven't answered all those questions and that's why we're being very careful about what we tell the public," Jones said.

Underwood, 34, is not married, Jones said. He said her son's father was among those being contacted by police, but he added that investigators had not narrowed in on any particular suspect.

Underwood is a co-owner of Boopa's Bagel Deli with Holly Pils, who said she last spoke with Underwood on Friday night.

"There's no one I know of that might want to do her harm," Pils said.

Two other Amber Alerts in Florida and Washington state were called off Monday. In Florida, two brothers, ages 7 and 2, allegedly taken by their mother from a relative's Panhandle home, were found safe in nearby Walton County. In Hoquiam, Wash., police found two young cousins unharmed at a home. The boys, ages 4 and 3, had been taken by the older boy's father.