A small but difficult fire continues to burn on and underneath the Ladner Creek Trestle Bridge outside of Hope two days after the historic bridge caught fire.

According to witnesses, on Sunday two men and one woman ventured across the dilapidated bridge and dropped a cigarette butt near the far end. By the time they returned, smoke was beginning to rise from the bridge deck.

"We asked them were you smoking out there and they said, 'shoot, that's not good,'" said witness Mallory Mogg.

"So they ran out there with water to try to put it out but it was too big by the time they got out there... and the water they had wasn't going to cut it."

"They left as soon as I called B.C. Wildfire," said Mogg.

Mogg said within 20 minutes the fire had grown from campfire size to bonfire size, and the planks of wood from the rail bed were falling into the forest below, lighting the trees on fire.

"So we called [B.C. Wildfire] back and said it was escalating, that trees were catching on fire and that everything was getting worse."

Mogg says a three person ground crew arrived 40 minutes later and air tankers about an hour later.

That's when the fire crews evacuated the area.

"They told us we had to go because it was getting unpredictable," said Mogg."Oh my gosh, there was so much smoke."

The Coastal Fire Centre says the fire is currently 0.2 hectares in size, but that steep terrain is making it difficult for the crew fighting it.

"They are focused on the area beneath the trestle, so we do have safety concerns for them going directly underneath because there's falling debris," said fire information officer Jeanne Larsen. "They are working to establish a water source and get in there and [get it] knocked down."

Larsen said the fire is "suspected person caused."

The Ladner Creek Trestle Bridge is about a 20 minute hike from a road just off the Coquihalla Highway. According to Mogg, the trail to the bridge has been getting busier in recent years.

"It's definitely gained in popularity," she said. "Social media makes it easier to share."

The Ladner Creek Trestle Bridge was part of the Kettle Valley Railway line through the Coquihalla Pass. Construction of the bridge was completed in 1916.