HOUSTON -- Texas Governor Greg Abbott Sunday said the state has activated 3,000 National Guard and State Guard members to take part in rescue operations as a result of severe damage and flooding from Hurricane Harvey.

A body was found not far from the coastal area in southeast Texas on Sunday, the sixth death reported after Hurricane Harvey made a landfall in Texas Friday evening.

Local police said they were not sure if the death was directly related to Harvey. "At this time it is unknown if the subject passed away from health conditions or due to drowning," police said in a statement, noting water in the area was high overnight.

At a Sunday press conference, Houston Mayor Sylvester Turner said more than 2,000 emergency calls had been received and more shelters would be opening.

The US Coast Guard has focused all its resources on rescuing people in trouble as waters continue to rise in Houston and surrounding areas, with assistance coming in from bases all over the country.

Eight helicopters and three flood response teams have rescued 100 people so far, officials said, and have received 500 calls for assistance.

The agency said that an additional 11 helicopters are expected. Another flood response team is coming from nearby Louisiana state.

About 80 counties have been declared state disaster zones. Both major airports in Houston have been closed amid severe flooding.

A Houston Airport System statement on Sunday said George Bush Intercontinental Airport and Hobby Airport are closed to commercial flights until further notice.

Widespread and worsening flood conditions prompted the closure of nearly every major road in Houston as the outer bands of Harvey swept through the area over the weekend.

Less than 24 hours after Harvey hit the Gulf Coast, more than 300,000 people were without power, according to AEP Texas, the transmission company that services the region hardest hit by the hurricane. AEP reported mass outages in areas along the Gulf Coast.

The loss of electricity was likely due to wind damage affecting more than 150 transmission circuits, according to the Electric Reliability Council of Texas (ERCOT), which oversees 90 percent of the state's electric grid.

Houston Mayor Sylvester Turner said Sunday morning the George R. Brown Convention Center has been opened as a shelter facility.

Hundreds of people sought shelters in the last 24 hours when Hurricane Harvey pummeled the Houston area.Latest news reports said the storm death toll has climbed to at least five.

The Houston government issued a notice Sunday morning that the 911 services are at capacity.

"If you can shelter in place do so, a few inches in your home is not imminent danger. Only call if in imminent danger."

Widespread and worsening flood conditions prompted the closure of nearly every major road in Houston as the outer bands of Harvey swept through the Houston area over the weekend.

As of Sunday morning, Houston TranStar has already logged 174 high-water road closures in the area.

The White House said Sunday that President Donald Trump will visit hurricane-ravaged Texas on Tuesday amid the ongoing recovery efforts.

President Trump, Vice President Mike Pence and members of Trump's cabinet discussed federal support for response and recovery efforts, said the White House. (Xinhua)