The party of Malawi's vice-president Saulos Chilima, who was killed this week in a plane crash, on Thursday demanded an investigation.
Chilima died on Monday alongside eight others when a military aircraft on an internal flight crashed into Malawi's Chikangawa Forest in dense fog.
His party, the United Transformation Movement (UTM), allied with President Lazarus Chakwera's Malawi Congress Party (MCP) in the 2020 presidential election, fielding a joint ticket.
But the alliance that brought the pair to office is now under pressure, with UTM leaders demanding answers from government ministers over the accident.
"We demand to know what happened to our leader. The plane had previously flown to Mzuzu under similar weather conditions," said leading UTM figure Stevie Mikaya, a regional governor.
"Was it a mechanical fault? Did it run out of fuel? We need the truth."
On Thursday, UTM members of parliament and party councillors sought to bar Minister of Defence Harry Mkandawire and Homeland Security Minister Ken Zikhale Ng'oma from attending Chilima's funeral.
At the party's headquarters in the capital, Lilongwe, Mikaya accused the ministers of negligence.
"It's disheartening that the plane crashed at 10:00 am, yet no action was taken to rescue those involved. We believe timely efforts from the ministers could have saved lives," he said.
MP Chrissie Kanyasho criticised the government's search efforts for the wrecked plane, which was only found on Tuesday.
"When we learned about the crash around 2:00 pm, we mobilised to search Chikangawa Forest," she said.
"We found only one military vehicle with nine soldiers searching the entire area, which was inadequate. The search for the vice president was handled as if they were looking for a lost goat."
Chilima, 51, who perished alongside eight others, including former first lady Shanil Dzimbiri, will be laid to rest on Monday in his home village in the Ntcheu district.
Initial reports had said 10 people died on the plane, but one of the names on the passenger manifest did not take the flight.
The plane, a Malawi Army Air Wing Dornier 228-202K, disappeared on Monday after it failed to land in the northern city of Mzuzu due to bad weather and was told to return to Lilongwe.
On Tuesday, President Chakwera said he had previously flown on the same aircraft for similar trips and the crew had successfully operated it just hours before the accident.
"And yet, despite the track record of the aircraft and the experience of the crew, something terrible went wrong with that aircraft... sending it crashing down," he said.
By Jack Mcbrams