HOUSTON -- The death toll from flash flooding in central Texas has risen to 87, with dozens still missing as search and rescue efforts entered the fourth day on Monday, according to local authorities.

Camp Mystic, a 99-year-old all-girls Christian summer camp along the Guadalupe River in Kerr County, grieved Monday the loss of at least 27 campers as well as counselors after heavy rains led to multiple flash floods in central Texas on Friday and Saturday.

Ten girls and a counselor from the camp were still unaccounted for as of Monday morning, Kerr County Sheriff Larry Leitha told a press conference.

Leitha said that as of Monday morning, 48 adults and 27 children were confirmed dead in Kerr County flooding, many of them pending identification.

Four other counties in central Texas have reported a combined total of 12 deaths, including several children.

"Our hearts are broken alongside our families that are enduring this unimaginable tragedy," the camp wrote in a statement on its website. "We are praying for them constantly."

Texas Governor Greg Abbott announced that US President Donald Trump on Sunday approved federal disaster assistance as part of a Major Disaster Declaration to unlock key federal resources for Texas.

In the meantime, criticism has been mounting over how the National Weather Service, whose budget and staff were cut under the Trump administration earlier this year, handled the emergency. Some local officials and residents said the flood warnings were late or insufficient.

Additional heavy rainfall is expected in the coming days, keeping parts of the state at risk for further flooding, according to Abbott.