Before Islamic State fighters gave up control of a northern Syrian stronghold less than a week ago, they left behind explosive dangers including booby traps in hospitals, an American combat medic told The Daily Beast on Tuesday.

Manbij, which lies on a supply route between the Turkish border and the de facto ISIS capital of Raqqa, fell to the Kurdish-led Syria Democratic Forces on Friday after more than two months of heavy fighting and U.S.-led airstrikes. The Britain-based Syrian Observatory for Human Rights says the fighting killed more than 1,700 people, including more than 400 civilians.

The Daily Beast reported that explosions continued to rock the city in the days after ISIS escaped -- and Kurdish fighters had to watch every move they made, because even black ISIS flags may have been booby-trapped.

"There are so many mines at this point that its almost on a ludicrous scale," Patrick Kasprik, a Floridian who volunteered as an SDF medic, told the website. "[The SDF] have set up small field hospitals for civilians, but with 100,000 residents returning to the city of Manbij, we need much more."

The capture of Manbij marked the biggest defeat for the extremist fighrers in Syria since July 2015, when they lost the town of Tal Abyad on the border with Turkey, analysts said, adding that hundreds of civilians ISIS used as human shields were freed.

Also over the weekend, the SDF announced a new campaign against al-Bab, a nearby town held by the extremists. The U.S. has provided the SDF with air cover and American special forces are advising them on the ground.

ISIS still controls large areas of Syria as well as Iraq's second largest city, Mosul. It has also claimed major terrorist attacks in recent months, including the Orlando massacre, the Nice truck attack, and a Baghdad bombing that killed some 300 people.

But Lt. Gen. Sean MacFarland, the top U.S. commander for the fight against ISIS, said this week that some 45,000 militants have been removed from the battlefield, reducing the group's total numbers to as few as 15,000.

The SDF launched its offensive in late May to capture Manbij under the cover of U.S.-led airstrikes.

Amateur videos posted online showed that shortly after SDF fighters captured the town late Friday, scores of residents went down to celebrate in the streets. Some men were seen clipping their beards with scissors while women were able to uncover their faces. ISIS imposes a harsh and extreme version of Islam on the territory under its control, including a mandatory dress code.

"May God destroy them. They slaughtered us," a young man shouted in a Manbij square. "May they not live for a minute."

In a photo posted online by Kurdish activists, a young woman defiantly uncovered her face while smoking a cigarette and flashing a victory sign. Under the extremists' reign, women had to wear long black cloaks that covered all but their eyes, while all adult men were forced to grow beards. Smoking was banned.

Kasprik reportedly traveled overseas in January while under threat of arrest for allegedly assaulting an officer in North Fort Myers, Florida.

The Associated Press contributed to this report.