The government advised the aspirants to maintain calm.
The protestors gathered outside the Union Public Service Commission (UPSC) office in central Delhi and raised slogans against the former Congress government for implementing CSAT in the examination pattern.
Policemen deployed outside the office used mild force to disperse them when they tried to cross the barricades.
A few protestors were detained and taken to a police station, police said.
Minister of State for Personnel and Public Grievances Jitendra Singh said the students should have some patience as the government is concerned about the issue.
"We are concerned about them and, in turn, they should also exercise restraint and have some patience as the government is already at it," he said.
"The youngsters should be advised not to cause any physical or mental agony or harm to themselves because the government is very much seized of the matter," he added.
Terming it a "conspiracy", former Bihar Chief Minister Lalu Prasad's son Tejashwi Yadav sought Prime Minister Narendra Modi's intervention in resolving the row.
"It seems to be a conspiracy against students from the economically-weaker sections especially the Hindi-speaking ones from northern India to keep them away from the civil services examination," Tejashwi Yadav said a letter dated July 27.
The letter was shared by Lalu Prasad on his Twitter account on Tuesday.
Bharatiya Janata Party leader Prakash Javadekar said: "The regional language level-playing field is an important issue... and therefore, we expect that the crisis will be over soon."
On Monday, 40 protesting aspirants were detained from near the same place after police used water cannons to control them.
The aspirants are continuing their protests at Mukherjee Nagar, a residential area in north Delhi near Delhi University popular with students who pour into Delhi from other states to prepare for the civil services examination.
The CSAT-II paper carries questions on comprehension, interpersonal skills, including communication skills, logical reasoning and analytical ability, decision-making and problem-solving, general mental ability, basic numeracy, and English language comprehension skills (of Class 10 level).
The aspirants have been objecting against the aptitude test and English language questions asked in the CSAT-II paper, claiming those were much above the standard prescribed for the examination.