They say the 19-year-old - named as Pouria Nour Mohammad Mehrdad - was probably migrating to Germany.
Investigations are continuing into a second man using stolen documents.
Malaysia Airlines Flight MH370 from Kuala Lumpur to Beijing went missing on Saturday, after taking off with 239 on board. The search has been widened.
Experts have said the presence of two people with stolen passports on a plane was a breach of security, but is relatively common in a region regarded as a hub for illegal migration.
Malaysia's police chief Inspector Gen Khalid Abu Bakar said the young Iranian was "not likely to be a member of a terrorist group", adding that the authorities were in contact with his mother in Germany, who had been expecting her son to arrive in Frankfurt.
Without a trace
The authorities' statement supports an account given to the BBC by a young Iranian in Kuala Lumpur who says he was a school-friend of one of the men who boarded the airliner using a stolen passport.
He says the friend and another Iranian, also using a stolen passport, stayed with him before taking the Malaysia Airlines flight, and that they had hoped to settle in Europe.
Reports from Thailand suggest that the tickets of the two men, routing them to Amsterdam via Beijing, had been bought through a Thai travel agent and an Iranian middleman.
Officials say they still have no idea what went wrong with the aircraft.
None of the debris and oil slicks spotted in the water so far have proved to be linked to the disappearance.
Four areas of investigation were focused on the possibility of human agency, the police chief said: hijacking, sabotage, psychological problems or personal problems with passengers or crew.
The passengers on the flight were of 14 different nationalities. Two-thirds were from China, while others were from elsewhere in Asia, North America and Europe.
At least 40 ships and 34 aircraft are taking part in the search in the seas off Vietnam and Malaysia.
Search teams from Australia, China, Thailand, Indonesia, Singapore, Vietnam, Philippines, New Zealand and the United States of America are assisting.
Malaysian civil aviation chief Azharuddin Abdul Rahman said the search was being conducted "on both sides" of the peninsula.
The area has been expanded from 50 nautical miles from where the plane had disappeared - over waters between Malaysia and Vietnam - to 100 nautical miles (115 miles; 185km)
据英国广播公司（BBC）报道，马来西亚警方3月11日称，持窃取护照乘坐MH370班机乘客是一名伊朗青年男子，与恐怖分子没有任何联系。
马来西亚警方表示，这位19岁的伊朗男子名叫Pouria Nour Mohammad Mehrdad，可能是想偷渡到德国去。
对另一名持假护照登机者的身份调查工作仍在进行中。
搭乘239名乘客的马航MH370班机在3月8日从吉隆坡飞往北京的途中突然失踪。目前，搜救规模正在不断扩大。
有专家此前表示，两人持偷窃护照登上班机的情况构成对航空安全的威胁，但是在一个非法移民猖獗的中心地区，这似乎也很正常，不必大惊小怪。
马来西亚警察总长Khalid Abu Bakar将军称，这名年轻的伊朗男子“不太可能是恐怖组织的成员”，并表示，有关部门已与他在德国的母亲取得联系，后者还一直期盼着与儿子在法兰克福机场相见。
杳无音讯
马来西亚当局的声明证实了此前一位伊朗年轻男子在吉隆坡向BBC的陈述。他声称是其中一位使用假护照登机者的同学。
他表示，在登上马来西亚航班前，他的同学和还有另外一个伊朗人住在一块。他们俩人都希望能到到欧洲落户。
来自泰国的报道表明，这两人从家泰国旅行社和伊朗籍的中间人手里购得经由北京飞往阿姆斯特丹的机票。
官员称，他们也不清楚飞机到底哪里出了故障。
目前，在水中发现的碎片和油迹都未被证实与失踪的飞机有关。
马亚西亚警察总长称，现在正集中调查四种人员犯罪的可能性：劫机，蓄意破坏，心理问题，乘客或者机组成员的个人问题。
这架飞机上的乘客来自14个不同的国家，三分之二的人来自中国，剩下的来自北美，欧洲和亚洲的其它地区。
在越南和马来西亚海域，至少40艘舰船和34架飞机参与了搜救。
参与搜救的国家主要有澳大利亚、中国、泰国、印尼、新加坡、越南、菲律宾和新西兰和美国也协助搜救。
马来西亚民航局长Azharuddin Abdul Rahman表示，搜救工作在相关半岛的“两面展开”。
搜救区域已经扩大到了飞机失踪地域方圆50海里——包括马来西亚和越南水域——到100海里。
