FORT BEND COUNTY, Texas - Hundreds of students at a Fort Bend County high school had to go to campus Thursday to have their blood drawn.

The students are among those suspected to have potentially been exposed to four active and contagious tuberculosis cases at the end of the 2017 school year at George Bush High School.

More than 650 students received letters initially requesting them come to campus for testing on June 19, but only 228 students actually went for testing.

Among them was GBHS senior Erlan Gomez who came to campus again on Thursday for the second round of tests.

"It was a pretty basic procedure,” said Gomez. "I’ve done it before I came the first time don’t know why they had to do it again.”

Only about 250 students had come for testing by midday Thursday afternoon, leaving more than 400 students still needing to be tested.

They will not be able to start the school year until they are tested for TB.

The ones who test positive for tuberculosis will have to go through a process which includes chest X-rays and antibiotic treatment until they are determined not to be contagious.

“If they’re positive and ill they’ll have to go through treatment before they’re allowed to come back to school,”said Fort Bend County HHS deputy director Kaye Reynolds.

George Bush High School will be open for TB testing until 7:30 p.m. Thursday night.

Sixteen people connected to the high school have tested positive for tuberculosis bacteria since June.