A park in the shadow of Yale’s Old Campus became the scene of a mass overdose on Wednesday as ambulance crews rushed from person to person, desperately treating dozens of semiconscious and disoriented drug users in New Haven.

More than 70 people overdosed in the city during a 24-hour span, beginning Tuesday evening, and the authorities said they suspect a virulent batch of synthetic marijuana, possibly laced with an opioid, was the cause.

The sheer number of overdoses caused a strain on the city, said Dr. Sandy Bogucki, the city’s director of emergency medical services. Emergency medical technicians, Dr. Bogucki said, were “sprinting from patient to patient in the park.” She said crews were transporting people more quickly than usual “just to turn the cars around and get them back out.”

Anthony Campbell, New Haven’s chief of police, said the first overdoses were reported around 8 p.m. on Tuesday at New Haven Green, a downtown park near Yale University. By Wednesday morning, the police said they were notified of several other overdoses from synthetic marijuana, also known as K2, or Spice, not only in the park but in three other locations around the city, including in the Fair Haven and Westville neighborhoods.