A law enforcement official familiar with the investigation told CNN there are believed to be at least four hostages, including a rabbi.
There are no injuries at this time, Nelson said, adding that police have evacuated the area.
“The FBI negotiators are the ones who have contact with the person in the building.” Nelson said. There is “no threat to the general public” at this time, Nelson added.
The hostage situation took place while the congregation was in the middle of its morning service, which was being livestreamed on Facebook.
The livestream appeared to capture part of the incident before it was removed. Law enforcement officials told CNN they reviewed the stream and are using it to gather clues on the incident and the individuals involved.
Police are asking people to avoid the area.
“We are currently conducting SWAT operations around the 6100 block of Pleasant Run Rd,” the Colleyville Police Department said. “All residents in the immediate area are being evacuated. Please avoid the area.”
“We ask that you continue to avoid the area. We will continue to provide updates via social media,” the police said.
Colleyville is located about 15 miles northeast of Fort Worth.
Congregation Beth Israel is affiliated with the Union for Reform Judaism, whose website indicates the congregation serves 157 membership families.
The synagogue, established in 1999 with 25 membership families, was the first Jewish congregation in Northeast Tarrant County, according to CBI’s website. The CBI community officially opened its doors to its own new building in 2005.
CBI holds Sabbath morning services every Saturday, and members and non-members alike are welcome to watch along from home on the livestream, a practice many synagogues have adopted in the wake of the pandemic.
CNN’s Shimon Prokupecz contributed to this report.