US President Donald Trump tweeted from Japan that he is monitoring the situation in Texas following a mass shooting at a church.
Trump, who's in Japan as part of a 12-day, five-country Asian trip, tweeted: "May God be w/ the people of Sutherland Springs, Texas.''
He added that the FBI is on the scene.
A spokeswoman said the federal Bureau of Alcohol, Tobacco, Firearms and Explosives was sending special agents from field offices in Houston and San Antonio to the site of the shooting in Sutherland Springs is south Texas.
A sheriff said a man walked into the church and started firing.
Authorities added the attacker is dead.
A Wilson County commissioner, Albert Gamez, told cable news outlets he was told it was more than 20 killed and 20 wounded.
One hospital about 10 miles from the shooting said there were "multiple'' victims with gunshot wounds being treated.
Connally Memorial Medical Center spokeswoman Megan Posey declined to say how many patients were being treated at the hospital, but said the number was less than a dozen.