A run-off presidential election between Tsvangirai and incumbent Robert Mugabe, who leads the Zanu-party, is set for June 27.
In recent weeks, both sides have accused the other of intimidating voters in an attempt to influence the vote.
George Sibotshiwe, a spokesman for Tsvangirai, told Al Jazeera that the MDC did not think that their leader would be charged with any particular offence.
"We suspect that he is not going to be charged at all; no charges have been brought against him yet," he said.
"The last time we were arrested, 48 hours ago, we were held for eight hours before being released.
"This is a deliberate strategy by Zanu-PF to disrupt Mr Tsvangirai's campaign and prevent him from having access to the Zimbabwean people.
"He was told he could campaign but only at his risk. [The authorities] do not want him to campaign because they know he has popular support."
Also on Friday, aid groups banned from working in Zimbabwe by the country's government were told that they can resume work if they promise not to interfere in politics.
Bright Matonga, Zimbabwe's deputy information minister, said that all non-governmental organisations [NGOs] in Zimbabwe had been asked to re-register, a day after the ban came into force.