A casino bus was clipped by a tractor trailer on I-95 this morning and sheered in half by a highway sign — leaving at least 14 passengers dead in the blood soaked wreckage just over the city line in The Bronx.

Most of the 31 Manhattan-bound bus passengers were sleeping at 5:30 a.m. when they were jarred awake to the terrifying scene.

PHOTOS: TOUR BUS HORROR

Cops believe a truck was changing lanes when it may have rear-ended the World Wide Tours bus, which was headed back from Mohegan Sun in Connecticut. Police were seeking the truck driver, who fled the scene.

The bus flipped onto its side and skidded down the highway, creating a trail of devastation in its wake as it slammed into the guardrail and the stanchion of a road sign that sheared the bus’ roof off as if it were a tin can, killing some people instantly.

FDNY Capt. James Ellson, 42, described a hellish scene of bodies and mangled metal as firefighters worked to free the survivors.

“It was just a pile of humans—on the seats, on the floor, wrapped around the wreckage,” the 20-year veteran said. “You have the live victims—looking at you, breathing, screaming in agony—with victims that had passed away, lying on top of them.

“The victims that were still alive were in absolute agony,” Ellson said. “It was more screaming than talking to us.”

Firefighters battled a gasoline leak from the bus as well as live electricity that made the scene even more treacherous.

The stanchion hit the upended bus “at face level” for the seated bus passengers, decapitating some of them, while at least one lost a hand, said witnesses who tried to claw through broken glass and twisted metal to reach survivors.

The impact of the accident sent passengers flying toward the front of the bus, while more than half a dozen others were pinned between the stanchion and the torn roof.

One passenger who gave his name as Victor said: “People were crying. People were screaming … I saw a lot of death.”

Police have a partial license plate for the tractor-trailer, NYPD Commissioner Ray Kelly said.

“We’re attempting to locate the truck driver,” Kelly said.

The death toll was expected to increase, said New York State Police Lt. Douglas Larkin, who described the situation as “still unfolding.”

Five survivors, including bus driver Ophadell Williams, 40, and a man on life support, were taken to St. Barnabas Hospital.

Williams, a married father of five from Brooklyn, was being tested for drug and alcohol use, police said.

Another St. Barnabas patient, also on life support, was unidentified and listed as Jane Doe, said Earnest Patti, head of emergency medicine.

“None of the family members have seen their loved ones yet because they’re still being evaluated,” he said.

At least seven victims were in serious condition at Jacobi Hospital, where people were searching for loved ones who may have been involved in the crash.

Many who were trying to confirm whether or not their relatives were even on the bus were hampered by the severity of the injuries involved, which made identifying the victims difficult.

Representatives from the Chinese consulate were also on hand.

Chung Ninh, 59, was sleeping toward the back of the bus when the crash woke him up. He was left dangling from his seat and clinging to it as the side of the bus flipped into the air.

“There was a lot of blood, all over the people,” he told The Post.

When he was able to escape the wreckage, Ninh tried to help others. He was checking one woman’s pulse when Williams, the bus driver, stopped him.

“The driver say: ‘She died, she died. Forget this one, help another one,’ ” he said.

Police were interviewing employees at World Wide Tours, which has a spotty safety record that includes two previous accidents.

In a statement the company expressed sorrow for the accident victims and promised to work with police.

“We will continue to use every resource at our disposal .¤.¤. to determine what happened,” a spokeswoman said.

The bus was carrying 32 people in all, including the driver. Many of the passengers were of Chinese descent and ranged in age from 20 to 50 years old. The bus had left Mohegan Sun at 3:45 a.m. and was heading for bus stops on Bowery and Allen streets.

Terrified relatives were also gathering at the NYPD’s Fifth Precinct looking for information about the victims, Kelly said in a news conference from the scene.

Mandarin and Cantonese translators were being brought to the local hospitals to communicate with the victims, Mayor Michael Bloomberg said.

“Our—and the entire city’s—prayers, thoughts and sympathies are with the victims, and their families and loved ones,” the mayor said.

The National Transportation Safety Board will help with the crash investigation, said Gov. Andrew Cuomo, who expressed condolences for the dead and injured.

“We also wish for the swift recovery of those who were injured, and thank the dedicated first responders who rushed to the crash site,” Cuomo said.

Victor was asleep in the back of the bus, and woke up after the crash.

“I saw people split open. It was awful,” he said.

“I tried to help people. Someone was crying for help … One man lost his hands. He was alive when the emergency people took him from the bus.”

Jose Hernandez, 49, was snoozing when the crash occurred.

“There were only eight people who survived, that were not dead or screaming for help,” he said. “We tried helping people, but there was a lot of twisted metal in the way.”

A limo driver heading northbound on the highway stopped and tried to help, only to find people keeping others away saying: “You don’t want to see this.”

All southbound traffic on Interstate 95 between exits 15 and 14 has been stopped as the investigation continues.

The scene was so gory that counselors were brought in to talk to the first responders who arrived at the crash site just inside the city line with Westchester County.

Additional reporting by Georgett Roberts, Jennifer Bain, Vinita Singla, Joe Walker, and Kevin Sheehan.