Members of Congress are asking the State Department how it will address a visa backlog that threatens to delay the enrollment of Indian students at US colleges and universities this fall.

The country accounts for the largest group of student visa holders, who contribute $9 billion to the US economy each year, according to a letter to Secretary of State Marco Rubio Thursday. Many of those students take part in basic research and cutting-edge inventions at universities in the lawmakers’ districts.

“We are dismayed at the possibility that many of these bright young individuals may be blocked—due to limited appointment …