Barbara Koster stands on her front door as she surveys her property which was left devastated by Hurricane Harvey in Rockport, Texas, August 26, 2017. [Photo/Agencies]

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

Local police said they are not sure if the death is directed 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 U.S. 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 state Louisiana.

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.