Mehmet Ali Ediboglu said Monday the group consists of 11 people of Sudanese origin, seven British citizens, two Sudanese, one American and one Canadian, who reportedly has Toronto roots.
Ediboglu had previously told The Associated Press that the group consisted of nine British medical students and doctors.
The lawmaker is helping family members of the group, who are in Turkey trying to find them. They believe the students have gone to Syria to provide medical assistance.
A Turkish official, who spoke on condition of anonymity because of rules requiring prior authorization to speak to the media, said Turkish police are working on the issue and co-operating with British authorities.
Ediboglu said ten of the students arrived in Istanbul from Khartoum, Sudan, early on March 12 and the Canadian arrived from Toronto. He said the group of 11 were all friends, and eight of them had graduated from medical school while three were about to finish.
The group spent a night in Istanbul, he said, before taking a bus to a southern province. Ediboglu said he suspects they crossed into Syria from the Turkish border town of Akcakale, across from Islamic State group territory, on March 13 or 14.
Members of the group have sent text messages to the families saying they are fine, he added.
"They say 'We're at the hospital treating patients,'" he said and the families took that to mean that they are in Syria.
Britain's Guardian reported that relatives searching for the group shared the Facebook profile photo of an Ismail Hamdoun and said he is a Canadian citizen.
The Facebook profile says he graduated from the University of Medical Science and Technology in Khartoum, Sudan, last summer, graduated from the University of Toronto in 2008 and from Bloor Collegiate Institute in 2004.
British member of parliament, Henry Bellingham, told the AP that one of the young women who entered Syria was the daughter of a respected surgeon at The Queen Elizabeth Hospital at King's Lynn, in England.
He said that the young woman had been "radicalized and exploited and swept away by other students" at the medical school in Khartoum.
Bellingham said Britain's Foreign Office has been in touch with them.
"It's going to be very difficult to do anything," he said. "It's a really dangerous situation and it's possible their lives are in danger."
He said the "air strikes are trying to avoid the main hospitals," suggesting the medics might not be in areas coming under attack by coalition forces. But he added he "wouldn't put it past IS" to deploy them in villages where they would be vulnerable to attack.
Gregory Katz in London contributed to this report
Follow Desmond Butler on Twitter at https://twitter.com/desmondbutler
With files from The Canadian Press