UPDATED: October 22, 2014, at 5:10 a.m.

Computer science, biomedical engineering, and mechanical engineering are the three undergraduate teaching areas at the School of Engineering and Applied Sciences whose faculty and facilities are slated to move to Allston in 2019, members of the school’s leadership said this week.

Applied mathematics, applied physics, electrical engineering, and environmental science and engineering, on the other hand, will remain in Cambridge during the so-called first phase of development.

A number of institutes and research centers will also relocate across the river, including the Institute for Applied Computational Science, the Center for Research on Computation and Society, and the Wyss Institute for Biologically Inspired Engineering's Cambridge-based division.

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In total, about two-thirds of SEAS faculty will relocate to the yet-to-be-built Allston campus as a result of this division, according to SEAS spokesperson Paul Karoff. The school currently has about 80 tenure or tenure-track professors and plans to expand that number by about 30 percent.

“Most of the determinations about Allston vs. Cambridge were straightforward,” Karoff wrote in an email.

The decision about who would move and stay was ultimately made by SEAS dean Cherry A. Murray following a discussion at the school’s May faculty meeting, according to Karoff.

He referenced the “unique facilities” based in Cambridge as a reason for determining which sectors relocated, mentioning in particular the Center for Nanoscale Studies used by several different FAS units, including parts of SEAS.

According to Physics professor and Area Dean for Applied Physics Eric Mazur, most physicists work at CNS on an almost daily basis.

“Relocating that facility would be impossible because it’s also being used by the Physics Department, by the Chemistry Department, by a number of even biology departments,” Mazur said, adding that Harvard invested hundreds of millions of dollars in the center.

Professor of atmospheric and environmental science and Area Dean for Environmental Science and Engineering Steven C. Wofsy said that the collaboration between his SEAS area and FAS’s Earth and Planetary Sciences Department constitutes an obstacle to moving.

“Almost everybody is jointly appointed,” he said. “So if EPS doesn’t move it doesn’t make any sense to move our area.”

However, he added that environmental sciences and engineering may move during a second phase of development of the Allston campus in about ten years.

According to Karoff, there is not yet a timeframe or definite plans for this second phase, even though it is a part of Harvard’s institutional master plan in Allston that the Boston Redevelopment Authority approved in 2013.