A woman whose husband and two children drowned in a pool while on holiday in the Costa del Sol is not satisfied their deaths were a simple accident and could seek further investigations, her lawyer has said.

Olubunmi Diya lost her daughter Comfort Diya, nine, her son Praise-Emmanuel Diya, 16, and her husband, Gabriel Diya, 52, in the incident on Christmas Eve at the Club La Costa World in Fuengirola.

Diya previously said in a statement all three could swim and claimed something was wrong with the Spanish hotel pool. Her lawyer, Javier Toro, said different engineers could be brought in for a parallel investigation after police said their findings pointed to the incident being an accident.

The hotel operator, CLC World Resorts and Hotels, said Diya’s claims were directly at odds with the findings of the police report. In a statement it stressed police findings made it “clear that their exhaustive investigations have confirmed the pool was working normally and there was no malfunction of any kind”.

An English translation of a Guardia Civil statement, released by the hotel operator, stated that tests had found no irregularity in the pool’s system. It said investigations indicated the accident was “caused by the lack of expertise of the victims when swimming”.

But Toro was quoted by the BBC as saying: “It’s very rare for three people to die in the centre of a swimming pool – especially in the case of a tall, hefty man. Something must have happened apart from a simple error or simple accident.”

He said the family was “not satisfied with the interpretation of it being a simple accident. Clearly the death of three people at the same time in a pool makes it evident that something very strange happened. It’s an event that must be studied.

“We do not discard the option of opening a parallel investigation through different engineers … to figure out what happened.”

According to the BBC, Toro said the family hoped to be given the detailed police report on the deaths next week.

Diya has said her family members were not left unattended and were somehow dragged into the middle of the pool. She said they followed the instructions displayed by the poolside at all times. Another daughter who was also on the holiday was unharmed.

About five well-wishers arrived at St Richard’s church centre, linked to Gabriel Diya’s religious group, in the hope of paying their respects to the family on Sunday morning, but left after it appeared no service would be taking place.

Outside the nearby family home, where flowers and cards were left by the front door, friends and family offered tributes. Olubunmi Diya’s childhood friend Elizabeth Moses-Mullard said they had exchanged messages since the incident. “It’s a really, really, very sad experience, it’s a traumatic experience,” she said. “I can only keep my thoughts and prayers with her.”

She said she felt upset and angry over the investigation into the incident so far, adding: “I want an independent investigation conducted and justice for my friend and her family.”

Olubunmi Diya’s cousin Doyin Akintokun called for a “good investigation” into what happened. “The damage is done – nothing can bring this family back,” she added.