The United Nations and human rights groups said they found "credible evidence" of the killings, while the United States and British embassies called for an investigation.
On Tuesday, the Myanmar government called diplomats to a briefing in Yangon to present what it said was evidence that the incident never happened.
But the government briefing failed to convince many who were present.
Correspondent: Jared Ferrie
Speakers: Kyaw Yin Hlaing, Rakhine State Investigation Commission; Lieutenant General Ko Ko, Myanmar's Home Affairs minister; Derek Mitchell, United States Ambassador; Wunna Maung Lwin, Foreign Affairs minister
JARED FERRIE: International diplomats and United Nations officials file out of Myanmar's foreign affairs ministry in Yangon.
They've just sat through a two hour briefing by senior members of Myanmar's government, which is keen to convince them that reports of an alleged massacre of at least forty Rohingya Muslims are false.
Kyaw Yin Hlaing is head the commission charged with investigating violence in Rakhine state where the alleged massacre took place.
He said the commission looked for mass graves, followed up on tips that Rohingya were abducted and tortured, and interviewed villagers looking for witnesses to violence.
KYAW YIN HLEING: We didn't really, at least we have yet to find concrete evidence that really indicate that something terrible might have happened to these people. The only clear evidence we could get was that the police sergeant was killed.
FERRIE: Lieutenant General Ko Ko, who is Myanmar's home affairs minister, said the incident began when police on a routine patrol confronted a group of Rohingya villagers.
KO KO (translation): About another 100 villagers armed with knives and sticks began attacking the patrol even though the team had identified itself. The crowd continued to grow and the patrol decided not to confront the mob. They decided to withdraw from the area. However, police say that [name of police officer] was left in the middle of mob with his M32 rifle. According to police officers who escaped they heard two shots from the village as they were leaving.
FERRIE: Everybody seems to agree that a police officer died in the January 13th clash with Rohingya villagers. It's what happened next that's at issue.
Lieutenant General Ko Ko said the police withdrew and called their local headquarters for reinforcements. He said police then returned and cordoned off the village while they began searching for suspects as well as the officer.
The United Nations and human rights groups said their investigations have turned up credible evidence that once the police returned in greater numbers, the killing began.
Reports of the alleged massacre were all the more easy to believe because it has happened before in Rakhine state.
Another problem with verifying reports from Rakhine state is that the government prevents access to many areas, including Maungdaw township where the alleged massacre took place. Journalists are barred completely and even aid agencies are severely restricted.
Myanmar officials promised to conduct a further investigation, but that didn't satisfy the concerns of some in the room.
During the question and answer session after the briefing, United States ambassador Derek Mitchell requested that the investigating team include at least one international member.
DEREK MITCHELL: What I would ask for then is, if possible, to have an international representative, a credible person from the international community who can take part and assist in that process and therefore reassure people on the ground in Rakhine, and the international community, that it's not simply the government investigating itself or the people investigating itself but that the international community can feel reassured.
FERRIE: It was a request that foreign affairs minister Wunna Maung Lwin politely declined.
WUNNA MAUNG LWIN: We will conduct the investigation in a very open and transparent manner, and we regard this as the internal affairs of Myanmar. I regret to say that we won't be able to include some of the representatives outside of the country.
FERRIE: The controversy continues over the alleged massacre and unless the government allows outsiders to see for themselves what happened, it's unlikely to be resolved.