Tech giant Amazon is expected to plant its first major Massachusetts flag at Riverfront Office Park near Kendall Square in Cambridge, according to real estate executives.

While exact numbers are not yet known, the Seattle-based company will likely occupy about 40,000 square feet at the office park, according to sources familiar with the expansion plans.

Another tech giant, Nokia, is scouring the Cambridge market for office space to establish a presence there. While neither company’s expansions are a done deal, industry executives said Nokia could land at Riverfront Office Park as well, taking about 60,000 square feet.

According to news reports, Amazon is planning to open a small office in the Cambridge Innovation Center in Kendall Square, where its logo now adorns a couple of office doors. But that is likely a mere placeholder until they can move into larger digs at Riverfront.

Riverfront Office Park, comprised of 1 and 101 Main St., holds 663,721 square feet of office space, according to a marketing flyer. Cushman & Wakefield is marketing the space for owner RREEF. The landlord is seeking rents more than $50 per square foot, though Amazon is sure to try to pay even lower prices, according to industry sources.

And in Cambridge, landlords have the upper hand when it comes to asking rates. There are currently only two properties in East Cambridge offering more than 40,000 square feet of contiguous office space. One is Riverfront, with about 93,000 square feet of contiguous office space, according to CoStar. CoStar also shows 156,000 square feet and 86,000 square feet of space being marketed at Riverfront Office Park, but a broker told Banker & Tradesman that deals could have been done recently to bring that down by more than 50,000 square feet.

The other property is 10 Canal Park, where Equity Office Properties is marketing the 118,000-square-foot building for lease since it planning to let the leases of the seven tenants that now call the property home expire in September.

There is also 81,000 square feet of space available at Four Cambridge Center in Kendall Square, but Boston Properties is saving that for an anticipated Google expansion.