Boston-based Square Robot has raised $5 million for its mini submarine-like robots that inspect the interiors of a variety of tanks used throughout the oil and gas industry.

The $5 million growth investment comes from Crosstown Capital LP, a Memphis, Tennessee, company that registered with the state of Tennessee in June. The deal gives Crosstown Capital managing partner, Milton Lovell, a seat on the Square Robot board.

The investment will help Square Robot expand its fleet of submersible robots from seven to 11. The company contracts the robots and an accompanying three-person crew to have the robot inspect above-ground tanks containing oil, diesel, jet fuel, gasoline, ethanol, water and other liquids, Square Robot’s chief growth officer Brian Kinsey told Hart Energy.

“They don’t have to drain the tank, they don’t have to vent the tank, so you’re containing emissions from fuels that are inside the tank,” Kinsey said.

He said the company’s goal is to build a fleet of 100 of these robots within five to ten years. The company said requests for robotic tank inspections have already surpassed last year by seven fold.