FBI agents raided a building Tuesday in Puerto Rico’s capital city of San Juan that is home to municipal offices associated with the administration of San Juan Mayor Carmen Yulin Cruz, a vocal political opponent of President Trump’s.

"More than 10" but "less than 50" agents based on the Caribbean island arrived at the Municipal Tower at 9 a.m. ET and were still conducting the operation as of 2:30 p.m. when FBI spokesman for the U.S. territory, Carlos Osorio, spoke by phone with the Washington Examiner in the afternoon Tuesday. Osorio described the operation as "pretty big."

Agents were seen entering the Municipal Tower with dozens of empty boxes. The federal agents deployed to the third, fourth, 14th, and 15th floors of the 16-floor building, Osorio said. They were looking for any paper and electronic documents related to "corruption" inside the city administration's purchasing and contracting departments.

The raid comes a month after Trump tweeted a quote from Fox Business anchor Lou Dobbs that said the U.S. territory’s government was "corrupt" while fuming over the raised death toll count in Puerto Rico from last year's Hurricane Maria.

"We have received allegations that they have been fixing contracts, that they are falsifying documents - these having to do with federal funds because if not, we would not have any jurisdiction," Osorio said. "They’re not directed at the mayor, but against people that work at the tower."

The allegations also include tampering with purchase orders and favoritism toward certain vendors.

Once all of the information is compiled and removed from the building, the FBI will go through the documents and determine if the allegations a former city worker made against others. The agents that participated in the Tuesday raid were from the agency's field office in Puerto Rico and regional task force.

Cruz’s office is located in city hall in a separate building from the one that was the focus of the federal agency’s attention Tuesday.

Cruz issued a statement on Twitter Tuesday morning saying all parties should cooperate with one another.

“At this time, members of the FBI are intervening in the Municipal Tower of SJ. My instructions as always are of total collaboration,” Cruz wrote, according to an unofficial translation. “I have no more information right now. We all have a duty to work together to clarify this situation."

"If someone has done something wrong, they must be subjected to due process and face the consequences of their actions," she added.

Trump and Cruz battled each other on Twitter late last year and into 2018 after the mayor alleged Trump was not doing enough to help the island after Hurricane Maria struck last September.