Immigration and Customs Enforcement (Ice) has arrested substantially more suspected undocumented immigrants during the first months of the Trump administration than during a similar time frame in 2016.

However, this total remains well below comparable time periods during the height of Barack Obama’s deportation drive, statistics released on Wednesday show.

The sharpest increase in arrest rates was among suspected undocumented immigrants with no criminal history.

In a highly unusual move, the federal law enforcement agency released details of the number of arrests it had made in a 98-day period under the new president. The agency usually releases such statistics on an annual basis unless it is compelled to produce them by freedom of information laws.

The data shows that in 2017, between 22 January and 29 April, Ice agents arrested 41,318 individuals, compared with 30,028 in an almost identical time period in 2016. The number arrested with no criminal history has more than doubled so far this year, from 4,200 between 24 January and 30 April 2016 to more than 10,800 in 2017.

This rise in the number of arrests among those with no criminal convictions marks a departure from Trump’s campaign pledge to target undocumented immigrants he branded serious criminals. It is probably a consequence of the president’s executive order, issued in January, that drastically expanded Ice agents’ powers, in effect allowing them to target any undocumented immigrant in the US, regardless of that person’s criminal history. The order reversed a 2014 homeland security policy, the Priority Enforcement Program (PEP), which instructed agents to target undocumented people with serious criminal histories for arrest.

Nonetheless, the total number of arrests in this 98-day period in 2017 is well below the total arrests carried out under the Obama administration before PEP was introduced. According to Ice statistics, provided to the Guardian on Wednesday, the agency arrested 64,903 suspects, including 16,877 with no criminal history between 20 January–29 April in 2013. In the same period in 2014, the agency arrested 54,584 suspects, including 14,702 with no criminal history.

Ice arrest data. Photograph: Guardian US

These statistics were not included in the agency’s release on Wednesday, which only included a year-on-year comparison.

If arrests were to continue at the same rate throughout 2017, Ice would end up arresting just over 150,000 suspects, with 26% of these having no criminal history, according to a Guardian projection. While this total would be much higher than in 2015 and 2016, it would be close to half the total in 2011 when, under the Obama administration, Ice arrested 288,392 suspects with 42% of those having no criminal history.

The presentation of the Ice data also marked a departure from standard norms at the agency. Previous Ice reports have used charts to describe the agency’s activities, but these graphics do not normally include a photo of an Ice official holding an upholstered firearm or a large image of an officer’s badge, as the chart released on Wednesday does.

The Ice spokesman Matthew Bourke said the agency’s decision to release data for an unconventional date range was due to “increased media interest”.

Brian Root, a quantitative analyst at Human Rights Watch, said the data “confirms the heartbreaking stories we are reading everywhere are not isolated instances – an increase in interior arrests, especially of people with no criminal histories.”

Root added: “Such enforcement will lead to more separated families and more damage to communities in which these immigrants have been contributing to for years.”