A fire at a popular nightclub in India's coastal region of Goa has killed 25 people, local officials say.

Police had initially thought a gas cylinder in the Birch nightclub's kitchen exploded – but the region's chief minister said on Sunday that this had been ruled out and that indoor fireworks were now thought to be the cause of the blaze.

The venue, located near a popular beach, was packed with revellers who had come to hear a Bollywood DJ. Four members of the same Delhi family and 21 staff died, police said.

Four people have been arrested, including the nightclub's manager, and an arrest warrant for the owner has also been issued.

Goa is a former Portuguese colony on the Arabian Sea. Its nightlife, sandy beaches, and resorts attract millions of tourists annually.

Eyewitnesses told the BBC of scenes of panic in the bustling nightlife area.

One said that he had been outside the club on what was a usual Saturday night with holidaymakers enjoying themselves when he heard screams.

"I didn't initially understand what was going on," he said. "In a bit, it became clear that a massive fire had broken out. The scenes were just horrific."

Though the main entrance is wide, the crossing over a small lake leading to the main structure is narrow and that made it difficult for firefighters to reach the spot.

The BBC saw what appeared to be melted remains of chairs, tables and plants in one corner of the club.

Goa's chief minister Pramod Sawant told journalists three people had died from burns, while most of the others had died of suffocation. Six people are in a stable condition in hospital.

Officials said 20 of the workers who died were from the Indian states of Jharkhand, Uttarakhand, Maharashtra, Assam, Uttar Pradesh, West Bengal and Karnataka. One worker was from Nepal.

A chef who works at a nearby venue told the BBC he knew some of the workers at the Birch club.

"People from all over the country and also from Nepal work in different clubs in Goa," he said.

"I am really worried for some people who I knew at the club. Their phones are off.

On Sunday, emergency teams were combing through the charred wreckage.

An inquiry into the cause of the fire has been launched, Sawant said, and a full report into the incident will be released within a week.

"Those found responsible will face most stringent action under the law – any negligence will be dealt with firmly," Dr Sawant added.

India's Prime Minister Narendra Modi called the Goa fire "deeply saddening" in a post on social media.

About 5.5 million tourists visited Goa in the first half of the year, government data showed, with 270,000 coming from abroad.

Some opposition politicians told the BBC that stricter regulations were needed to avoid such tragedies.

They alleged that newer clubs were opening too frequently and the government needed to ensure they were safe for people to visit.

India has seen a number of deadly fires at entertainment venues in recent years.

A fire at a three-storey building killed 17 in the southern city of Hyderabad in May, while a hotel blaze in north-east Kolkata left 15 dead a month earlier.

Last year, 24 died at an amusement park arcade in the western state of Gujarat after visitors were trapped inside. An official review later found poor safety standards contributed to the death toll.