FALFURRIAS – It’s a search mission that some days won’t end in a rescue. That was the case Tuesday for U.S. Customs and Border Protection Air and Marine Operation agents. The crew took to the sky after getting a 9-1-1 distress call.

Two immigrants were in need of help. One of them was unresponsive.

The adapted black hawk helicopter gives agents plenty of room in the cabin and endurance for long flight times other planes lack.

Jeff Bujanos, Aviation Enforcement Agent, said time is already an enemy by the time they get the call.

“Ninety-percent of the time when they call, they've been in the brush for two days. They've been in the brush for three days. They don't have any food, they haven't had any water, the guide just left them,” said Bujanos.

In August, agents saw a rise in 9-1-1 distress calls.

"We were swinging through Falfurrias, in Brooks County. The 9-1-1 call center got a 9-1-1 call for two persons in distress out in the ranch area, one of which was unresponsive. In its truest sense, a medical emergency," said PJ Welch, marine interdiction agent.

Communication is often delayed in these scenarios. Factor in the broken signal and the chain of contact, and you’ll realize it’s a tough mission.

The call was answered by the Brook’s County Sheriff’s Office, they contacted border patrol, who then contacted the 9-1-1 call center, then information reached Air and Marine Operations.

The GPS coordinated provided to agents from the 9-1-1 call center aren’t specific. This means, rescuers have limited details of where those in need of help may be.

“There's miles and miles and miles of nothing there. So a lot of times what they'll do is they'll say I’m by a windmill. Well if you're in the air at 500 feet, looking at windmills, each farmer has a windmill on the farm so there could be 10-20 windmills. So we have to go from windmill to windmill to windmill to see where they are at," said Bujanos.

On Tuesday, agents were in the air for nearly four hours trying to locate the two men. With gas running out and nightfall approaching, the rescue mission was suspended.

"In a way I feel disheartened that we didn't make the rescue, but it also reminds me how privileged I am to live in this country and that's something that I think most people today take for granted today," said PJ Welch, marine interdiction agent.

The two immigrants who crossed the border illegally will have to wait a little longer. The next crew tried their luck with an added obstacle - the darkness of night.