His son and the New York-based Center for Human Rights in Iran say that authorities told Seyed-Emami's family that he committed suicide in custody, something they described as suspicious following other detainee deaths.
In a statement earlier on February 11, Tehran's Chief Prosecutor said that Seyed-Emami committed suicide due to confessions made against him.
Yasamin Alttahir, Middle East and North Africa spokesman at Amnesty International, told Al Jazeera on Monday that the rights group too supports an independent investigation on Seyed Emami's death.
"Some of them refused to comment, some others said we pursued (but) failed to get information", the lawmaker wrote.
Erik Solheim, head of the United Nations Environment Programme, said on Monday that he is "shocked and saddened" by the news of Seyed Emami's death. "I still can't believe this", he wrote late on February 10, adding that the family was asking for an independent autopsy.
Among them was Hooman Jokar, who headed a programme to save the endangered Asiatic cheetah.
In November, the conservative-linked Tasnim news agency accused Tahbaz of being a big-game hunter who was trying to seize control of national park land in northern Iran.
An Iranian-Canadian university professor detained in Tehran has died in custody, activists and a family member said Sunday, marking the latest suspicious death of a detainee in Iran after a crackdown on dissent following nationwide protests.
The most recent arrests also suggested that environmental issues - a spark for the recent protests - were becoming increasingly politically sensitive in Iran.
A senior official at the EPO, who did not wish to be named, told AFP on Monday that this was incorrect and that Madani was at work. He had a quite eclectic set of interests from economics, politics, very much the environment, he was a very well-rounded sociologist.
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"The claim of a suicide is highly questionable", Ghaemi said in a telephone interview with The Canadian Press, while admitting he had "no idea" how the professor may have really died.
"The Tehran prosecutor's incomplete and vague information has added to these concerns".
In another development, Kaveh Madani, the deputy of Iran's environment department, was reportedly imprisoned, according to Mahmoud Sadeghi, a parliament member allied with President Hassan Rouhani.
"He came back recently from Canada where he was doing research". What is going on in this country?
Many also raised questions about the fates of as many as seven of Seyed-Emami's fellow environmentalists who were said to have been detained as well, after officials accused them publicly of collecting "classified information about the country's strategic areas under the guise of carrying out scientific and environmental projects".
That case weighed on Iranian-Canadian relations for years. A spokesperson for Foreign Affairs told CBC News in an emailed statement that consular officials "are working to gather additional information and are providing assistance to the family of the Canadian citizen".
The Canadian government is calling on Iran to conduct an investigation into the death of an Iranian-Canadian professor, who died in a Tehran prison after his arrest on allegations of spying last month. "On his return, he was called in several times" by the authorities.
Seyed-Emami was injured after volunteering and fighting on the front lines of Iran's bloody 1980-88 war with Iraq.
The vice-president at the time, Mohammad Ali Abtahi, stated she died from "a brain hemorrhage caused by a beating".
Although Mr. Alghabra said the investigation should address the cause and circumstances surrounding Mr. Seyed-Emami's death, it's not clear if Canada specifically asked for an autopsy.