  We present families of pairs of finite von Neumann algebras $A\subset M$
where $A$ is a maximal injective masa in the type $\mathrm{II}_1$ factor $M$
with separable predual. Our results make use of the strong mixing and the
asymptotic orthogonality properties of $A$ in $M$ and are borrowed from ideas
of S. Popa who proved that if $G$ is a non abelian free group and if $a$ is one
of its generators, then the von Neumann algebra generated by $a$ is maximal
injective in the factor $L(G)$. Our results apply to pairs $H<G$ where $H$ is
an infinite abelian subgroup of a suitable amalgamated product group $G$.
