Firefighter injured dousing Houston blast flames (VIDEO)

A fire has broken out at a building in downtown Houston, with a witness reporting that he heard an "explosion," according to local media. Footage from the scene shows the flames billowing from the windows of the premises.

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The incident occurred at offices belonging to Lone Star Legal Aid on Fannin Street, according to ABC 13.

A photo posted on social media shows a fire truck battling the blaze.

One firefighter was injured while hosing down the blaze, KPRC reporter Haley Hernandez tweeted, adding that he had been taken to a nearby hospital. 

Hernandez said the building is next to a daycare center.

The fire has reportedly been extinguished, a senior executive producer for local news outlet KPRC 2 tweeted. 

Lone Star Legal Aid tweeted hours before the fire that its Houston office would be closed Monday, due to Tropical Storm Harvey. 

The fire comes as Houston struggles to cope with massive flooding inflicted on the city by Hurricane Harvey which has since been downgraded to a tropical storm.

As the city braces for more heavy rain and flooding in the coming days, the US Army is releasing water from two local reservoirs which have risen too quickly as a result of Harvey. 

The Federal Emergency Management Agency (FEMA) has said it is working to assist people in the area, noting that 450,000 people are likely to be in need of help. More than 30,000 are expected to be placed in temporary shelters.