A plane electromagnetic wave propagating along x-direction can have the following pairs of E and B

E, B and velocity of electromagnetic waves are mutually perpendicular to each other.

$\hat{\mathrm{E}}=\hat{\mathrm{B}}\times \hat{\mathrm{C}}$

$\hat{C}=\hat{E}\times \hat{B} \Rightarrow \hat{i}=\hat{E}\times \hat{B}$

So, Electric field is along y-direction and magnetic field is along z-direction.

or, $\hat{C}=\hat{E}\times \hat{B} \Rightarrow -\hat{i}=\hat{E}\times \hat{B} \Rightarrow \hat{i}=\hat{B}\times \hat{E}$

So,  Electric field is along z-direction and magnetic field is along y-direction.

Hence, Electric field and magnetic field can be along y- or z- directions.