It’s one of life’s simple truths. If you don't pay your credit card bills on time, eventually the credit card company will cut you off.

The people who run Dallas County learned that the hard way recently when the credit cards they were late paying were the ones used to fill police and fire vehicles with gas.

The result was nearly three days of frustration and concern as well as a potentially dangerous situation.

Deputies with the Dallas County Sheriff’s Office drove miles in search of fuel. Firefighters reached into their own pockets to gas up their trucks and there was a flurry of e-mails between county officials demanding answers for how this could happen.

It all started at the beginning of the President’s Day weekend in February, when Dallas County sheriff’s deputies discovered their county-issued gas cards were being declined all over town.

“It's really hard to do your job when your car is not going to go anywhere”, said sheriff’s union leader Scott Guiselman.

As that long holiday weekend began, Guiselman started hearing from deputies wondering what was happening. Records obtained by NBC 5 Investigates show a flurry of emails from county officials wondering the same thing.

By early Saturday morning a sheriff's sergeant said in an e-mail, "We have been unable to refuel any of the cars that 1st watch had used. Not sure how it will get fixed."

Another sheriff's official emailed to say he called the after-hours number on the fuel card and was told, "The county had over run its credit and we were cut off. Basically they didn't pay the bill."

“We’re the second largest county in Texas, there's no excuse for this at all,” said Guiselman.

With no other way to obtain fuel, deputies scrambled to open up a county service center that normally is closed on weekends. The service center has its own gas pump, but is in Garland many miles from the areas many deputies patrol in the south and west portions of the county. So deputies had to drive a long way to re-fuel three times a day, or at the end of each shift.

“You're going to be involved for at least an hour going there and back. So that takes you off the street for an hour”, Guiselman said.

Asked if pulling deputies off the street to get fuel creates a safety concern Guiselmen responded, “Absolutely. Now there's guys involved for an hour a day going to get fuel instead of working crashes or enforcing laws on the freeways.”

As the hours passed, the e-mails show frustration grew.

By Sunday, Dallas County Sheriff Lupe Valdez fired off an e-mail simply telling staff, "Get ahold of the purchasing guy and get them fuel!"

And it was more than just sheriff’s deputies affected. Other county vehicles use the same cards, including courtesy patrol trucks that help stranded drivers, Parkland Hospital Police and county fire trucks.

“I'm concerned that this happened. It should not have happened”, said Dallas County Administrator Darryl Martin.

Martin admits the county got behind on paying the bill.

“We had some accounts that they said were delinquent,” Martin said. “So all of the sudden we got hit and they cut us off.”

Martin said part of the problem was that Fuelman -- the county’s gas card provider -- recently sold its Dallas operations to another company called FleetCor.

County commissioners still needed to sign off on recognizing FleetCor as a vendor -- before the county could write FleetCor checks.

“If they had called, if we had conversations, we would have assured them that payment was going to come,” Martin said.

County e-mails show FleetCor did send the county an email saying "Please call regarding past due," four days before the shut off.

By then the county owed more than $100,000.

Still, Martin believes it was irresponsible for FleetCor to cut off a county where emergency responders rely on their cards for fuel.

“We take some responsibility, and FleetCor should certainly take some responsibility,” Martin said.

In a statement to NBC 5, FleetCor told us the county was cut off "...due to credit limit overages which were set up as a protective security measure. This matter was addressed in a timely manner and no further service disruptions have been reported,” the statement said.

But as the hours dragged on that weekend, and deputies crisscrossed the county for fuel, officials worried what might happen if there was a major incident.

Less than two months earlier the county had suffered devastating tornadoes that kept emergency responders running nonstop.

“Fortunately nothing did happen, but it could have,” Martin said.

By Monday, the President's Day holiday, two and a half days after the cards were cut off, a sheriff's staffer reported in an e-mail, "Fuelman is back on."

A top sheriff's commander responded "Yeah!!"

But Dallas County Commissioner John Wiley Price chimed in saying, "It's not enough that they are back on, what the hell happened?"

Martin credits quick-thinking sheriff’s deputies for averting a crisis along with people like the county firefighters who sent an email reporting a fire captain went ahead and paid for the fuel for his truck out of his own pocket.

“God bless those guys,” Martin said. “They saw how important this was and they're going to get reimbursed.”

Martin said the county plans to negotiate a new fuel card contract soon. One that would require much more notice before the card company can cut them off -- especially on a holiday weekend.

Martin said he has also talked to staff about the importance of communicating with vendors if a payment is going to be late in order to avoid any other potentially risky situations.

NBC 5 Investigates checked with other counties in the DFW area to see if their first responders have ever experienced similar problems. Officials in Collin, Denton and Tarrant counties said their first responders typically fuel up at county-owned pumps at the start of their shifts and only use fuel credit cards as a backup in case they’re not close to a county service center.