2001 Infiniti I30

2001 Infiniti I30 6 cyl Automatic 110000 miles

I tried to put gas in my car and was unable to get it to go in. If I pumped it very slowly I could get a little in but it kept running backout of the tank. Its at a repair shop now. They have took the gas tank off and checked the hoses and found nothing. They were able to get about $7 in before it started running back out the tank again. Any ideas as to what could be causing this, there pretty much at a loss at the repair shop. Thanks