HOUSTON, May 10 (UPI) -- U.S. immigration officials Saturday were processing 89 illegal immigrants arrested in Houston during a four-day operation this week, officials said.

Officials were also working on a backlog of 30,000 immigration fugitives in southeast Texas, the Houston Chronicle reported.

"We're continuing to move forward with their removal process," said Greg Palmore, spokesman for U.S. Immigration and Customs Enforcement in Houston.

"We're doing this every day; this is not an isolated surge," he was quoted as saying. "There are four active fugitive operations teams that are out there working in the same capacity every day."

The operation, which began early Tuesday and ended Friday, netted a total of 89 illegal immigrants. Of those arrested, 28 had criminal convictions.

Kenneth Landgrebe, field office director for ICE detentions and removals in Houston, stressed the operation was not part of "mass raids" against illegal immigrants.

"These are not roundups," he said. "These are targeted individuals that have had their day in court and have refused or failed to leave as the courts have ordered."