The Pakistani national, Mohammed Saif Ur Rehman, who arrived in Chile four months ago to study tourism, was detained on Monday when he entered the US mission to process a visa.

“There were indications of an explosive substance on his clothes,” a police spokesman told Reuters. Police gave no details on how the substance was detected but a local newspaper said the embassy has an explosive-detection system.

The police spokesman said authorities had searched the student’s lodgings in the capital overnight and that he would be brought before a judge on Tuesday to make a statement.

Pakistan continues to be a major security issue for the United States. Faisal Shahzad, a Pakistan-born naturalized American charged with trying to set off a car bomb in New York’s Times Square this month, has admitted to being trained in a Taleban stronghold in Pakistan.